1. Field of the Invention
The invention relates to the field of masking. Masking is understood to mean a step in a method of treating a surface in which at least part of the surface that is to be treated is covered, generally temporarily, so as to spare that surface from the treatment.
The invention relates to a method of masking and to a method of painting at least part of a motor-vehicle, and also relates to an adhesive masking strip suited to said methods of masking and of painting, and to a method of manufacturing said strip.
2. Description of the Background
Methods of masking are commonly used in all kinds of industry, for example in those in which a method entails a painting step, particularly in automotive repair.
Such methods and associated adhesive masking strips are described ire particular in the following documents: EP-B-0 365 510 and EP-B-0 384 626. EP-B-0 355 510 describes a method of masking which comprises the use of an elongate, compressible and flexible wad of cellular material which is resistant to a surface treatment for masking at least part of a surface that is to be treated. The wad of cellular material is applied to the part of the surface that is to be treated and is detached after the treatment has been completed. Said wad of cellular material constitutes an adhesive masking strip. This strip is arranged along the surface that is to be treated by hand or by using a tool that allows the strip to be distributed.
It is clearly apparent from the description and from the figures that the adhesive masking strip described in that document is of roughly cylindrical or parallelepipedal geometry and that it is arranged on the surface that is to be treated using pressure applied to the exterior face of the strip, the opposite face to the adhesive face which is placed in contact with the surface that is to be treated.
EP-B-0 384 626 describes foam items made of cold-weldable foam which can be used as adhesive masking strips. As before, the geometry of these strips is roughly cylindrical and they are applied by pressing on the exterior part of the strip, on the opposite side to the adhesive-coated part.
This type of strip, although very commonly used, particularly in the field of automotive repair, has several disadvantages.
On the one hand, positioning the strip on a surface that is to be masked is made difficult by the geometry of these strips in the case of certain parts that need to be protected. The problem is that the shape of the bodywork is highly diverse and tends to be increasingly complex, particularly with the edges of bodywork parts forming curves with small radii of curvature, or even exhibiting acute angles. This being the case, it is difficult to position the adhesive masking strips defined hereinabove and to press them down at the same time in order to apply them. It is generally necessary to use several fingers of one or even two hands in order to makes theses strips follow the edges of bodywork for which protection is intended. The geometry of these strips, cylindrical or parallelepipedal, allows a limited radius of curvature and it is necessary to force the deformation of these strips, or even to cut into them in order to makes them follow a complex path.
It sometimes happens that strips fitted in this way under high stress relax and no longer follow the desired path. They then have to be detached and repositioned, which is a time-consuming operation. Furthermore, the strip does not stick as firmly to the surface that is to be treated and there is a risk that it will move, which may give rise to defects, particularly paintwork defects during subsequent surface-treatment operations.
Another problem associated with the adhesive masking strips mentioned hereinabove stems from the fact that the geometry of such a type of strip does not suit it to all the parts in a vehicle for which protection is intended. The problem is that the adhesive masking strips may be used to protect a space between a moving part and a fixed part of a vehicle. A fixed part is understood to mean the parts of the bodywork that form the structure of the vehicle, particularly the body, the fenders, the pillars and the roof, whereas the moving parts are understood to be parts which can move with respect to the fixed parts, particularly doors, a hood and a tailgate.
Now, the separation between the various fixed parts and the various moving parts differs very appreciably from one part of the same vehicle to another.
To protect part of the vehicle by masking, particularly before putting it in for painting, it is necessary to seal this space off against paint, something which as obtained by slightly compressing the adhesive masking strip arranged on a fixed or moving part against the other part, moving or fixed respectively. The adhesive masking strips described hereinabove are generally unable to suit all the spacings that may be encountered on a given vehicle, and even more so on vehicles of different types. It is therefore necessary to uses several sizes of one type of adhesive masking strip in any automotive repair shop, or even for preparing a single vehicle. For a given type of strip, the overall shape of different strip sizes is roughly identical, only the dimensions of the strips used to suit the various spacings varying. The differences in size between strips of the same type, particularly the largest dimension in the cross section of such a strip, may be as high as a factor of two. It is commonplace to find, in a repair shop, adhesive masking strips of this same type in three different sizes. This results in significant stocks and multiple handling operations.